The present invention is directed, in general, to winding configurations for inductive devices and, more specifically, to a winding configuration for an inductor reducing or minimizing external magnetic fields.
Many configurations for the windings of an inductor around a core or form have been proposed or employed. The simplest and most common configuration involves progressive windings around the radial circumference of a cylindrical core or form. Alternative configurations, usually designed to maximize magnetic flux and/or inductance, increase sensitivity to electromagnetic waves, or reduce Lorentz forces, include toroidal windings (progressive windings around a doughnut-shaped core or form) and similar variations.
In borehole production, inductors are employed for filtering electric (normally three phase) power to be transmitted into the borehole. Surface voltage magnitudes of the electric power may equal or exceed 10 kilovolts (kV), with associated, proportionally high currents. For inductors having conventional configurations, such high currents through the windings can produce intense magnetic fields external to the inductor. The external magnetic fields, in turn, induce eddy currents within surrounding metals and conductors and, because of resistance, generate undesirable heat. As a result, cabinets for enclosing surface power equipment for borehole production systems must be made larger to provide extra distance so that the intense magnetic fields produced by the inductor do not produce significant eddy currents within the cabinet walls.
There is, therefore, a need in the art for a low external field inductor for use with borehole production electric power systems.
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide, for use in borehole production system, an inductor which is wound axially around a cylindrical center structure, such as a core or form, so that each turn includes portions extending axially along a circumferential outer surface of the center structure and portions extending across the end surfaces of the center structure. Adjacent axial portions, which are preferably but not necessarily consecutive turns, carry current in the same direction to the extent possible. External magnetic fields therefore fall off rapidly and at least partially offset so that the inductor can handle high currents such as those relating to filtered electric power transmitted into a borehole for powering artificial lift equipment.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art will appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words or phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprise,xe2x80x9d as well as derivatives thereof, mean inclusion without limitation; the term xe2x80x9corxe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewith,xe2x80x9d as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, whether such a device is implemented in hardware, firmware, software or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases.